Case-harbenxhg steel



UNITED STATES PATENT OFFICE.

JOHN D. CUTTER, OF BROOKLYN, NEW YORK, ASSIGNOR T0 CLIMAX MOLYIBDENUM COMPANY, A CORPORATION OF DELAWARE.

CASE-HARDENING STEEL.

No Drawing.

To all whom it may concern:

Be it known that 1, JOHN Drcns CUTTER, a citizen of the United States, residing at Brooklyn, in the county of Kings,-State of New York, have invented certain new and useful Improvements in Case-Hardening Steel; and l do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to an improved case hardening steel and to articles made therefrom.

The improved case hardening steel of the present invention .is a nickel-chrome-molybdenum steel containing 1% or less of each of these three metals. It is of particular advantage for use in making articles, such as gears, which require case hardening, and where superior wearing properties of the case hardened surface, combined with a tough core, and the property of quenching without appreciable deformation, are important.

The case hardening steel of the present invention, as above noted, contains nickel, chromium and molybdenum, in amount from a substantial fraction of 1% up to 1%. It is also a low carbon and low manganese steel containing less than 0.30% carbon and, in most instances, less than 0.25% carbon, and usually less than about 0.5% manganese as well asless than about 0.25% silicon and around 0.06% or less of sulfur and of phosphorus. It will be understood, however, that these ingredients, which are common to all low carbon steel, are capable of some variation.

While some variation in the percentage of nickel, chromium and molybdenum is permissible, all three of these metals will be present only in small amount, 71. 6., 1% or less. For many purposes, it is advantageous to have a nickel content of the steel as low as 0.5% or lower, and a satisfactory case hardening steel can be made containing chromium and molybdenum in amounts of 1% or less, and nickel in amount equal to 0.5% or less. Again, somewhat higher percentages of nickel are permissible where the molybdenum is around 0.5% or less. For example, the nickel may vary from 0.4 to 0.8%,-

the chromium from 0.4 to 0.9%, and the mo- Specification of Letters Patent.

Patented Nov. 116, 1920.

Application filed June 28, 1920. Serial No. 392,233.

lybdenum from 0.25 to 0.5%. All of these steels are low carbon steels, so that, when subjected to case hardening, the core will be of low carbon content, and sufiiciently tough. The steel compositions above referred to are especially adapted for the production of suitable case hardened articles, being characterized.- by ease and rapidity of penetration during case hardening, and iving a hard case without objectionable eformation, while the core, owing to the com position of the steel, will retain the degree of toughness desired in case hardened articles.

The steel which T particularly recommend Such a steel can be readily machined and used in the production of various articles, especially gears for automobiles and the like, and such articles can then be subjected to case hardening in a manner which will be readily understood by those skilled in the art. The case hardening operation can thus be carried out with different case hardening agents, and at different temperatures and for different periods of .time, depending upon the particular case hardening process employed, the depth of penetration required, etc. It is a characteristic advantage of the case hardening steel of the present invention that the carbon penetrates readily so that the case hardening operation can be effected with a substantial economy of time. The time will of course vary somewhat with the depth of case required.

The improved steel of the present invention is well adapted for quenching in oil to give a sufficiently hard wearing surface or case together with a tough core, and without objectionable shrinkage or deformation during the quenching. The composition of the steel is such that, even with the slower cooling which takes place in oil, as distinguished from water, the cooling is nevertheless sufficiently rapid, and the other changes that take place during hardening are so modified, that the desirable qualities above referred to are nevertheless obtained. The improved steel of the present invention is thus of special value for use in automobile gears, and the resulting gears made therefrom are characterized by the properties above referred to.

I am aware that nickel-chromium-molybdenum steels have heretofore been proposed, but it has always been considered necessary, so far as I am aware, to use an amount of nickel considerably in excess of that characteristic of the present invention, for example, from 2 to 5% of nickel, or such steels have in other respects differed in their composition and properties from that of the present invention.

1. A case hardening steel low in carbon and containing nickel, chromium and molybdenum, each in substantial amount not exceeding 1%.

2. A case hardening steel low in carbon and containing small amounts of nickel, chromium and molybdenum, the amount of chromium and molybdenum being less than 1% and the amount of nickel being less than about 05%, said steel being characterized by ease of penetration of carbon during case hardening, and giving a case hardened article which can be quenched without objec-v tionable distortion to give a finished article with a hard wearing surface and tough core.

3. A case hardening steel containing nickel, chromium and molybdenum in substantially the following proportions:

Nickel 0.40% to 0.80 Chromium 0.40 to 0.90 Molybdenum 0.25 to 0.50

said steel being characterized by ease of penetration of carbon during case hardening, and giving a case hardened article which can be quenched without objectionable distortion to give a finished article with a hard wearing surface and tough core.

4. A case hardening steel containing nickel,

chromium and molybdenum in substantially the following proportions:

Nickel 0.40 to 0.60% Chromium 0.45 to 0.65 Molybdenum 0.25 to 0.35

said steel being characterized by ease of penetration of carbon during case hardening, and giving a case hardened article which can be quenched without objectionable distortion to give a finished article with a hard wearing surface and tough core.

5. A case hardening steel containing the following ingredients in substantially the following proportions:

Nickel 0.40 to 0.60% Chromium 0.45 to 0.65 Molybdenum 0.25 to 0.35 Carbon 0.10 to 0.20 Silicon less than 0.25 Manganese 0.30 to 0.50 Sulfur 0.06 to less Phosphorus 0.06 to less Nickel 0.40 to 0.60 7c Chromium 0.45 to 0.65 Molybdenum 0.25 to 0.35

said article having a tough core and a hardened case.

In testimony whereof I afiix my signature.

JOHN D. CUTTER. 

